US2211691A - Transformer construction - Google Patents

Description

Aug. 13 9 0- R. s. EDWARDS 2,211,691

TRANSFORMER CONSTRUCTION Filed Sept. 17, 1938 2 Sheets-Sheet l INVENTOR 1 055427 8. foam/e05 1 5 BY 1 A 33 MI W ATTO NEY R. 5. EDWARDS TRANSFORMER CONSTRUCTION Filed Sept. 17, 1938 Aug. 13, 1940.

2 Sheets-Sheet 2 llm mum INVENTOR P0552? S 'qa/Ae s Patented Aug. 13, 1940 UNITED STATES TRANSFORMER CONSTRUCTION Robert S. Edwards, New Canaan, Conn, assignor to Edwards and Company, Inc., Norwalk, Conn, a corporation of New York Application September 17, 1938, Serial No. 230,377

14 Claims.

This invention is concerned with transformer construction and installation, particularly of the low voltage type of transformer, such as is employed in obtaining lower voltages from the usual type of household lighting or power circuit which is usually of 110 volts.

One of the objects of this invention is to provide a transformer and installation construction whereby cost of manufacture and cost to the consumer may be reduced, manufacturing processes simplified, quicker assembly in manufacture achieved, and less cost and greater flexibility and adaptability of installation achieved. Another object is to provide a transformer construction capable of manufacture with a minimum of tools and hence tool cost, and yet capable of meeting varying requirements. Another object is to provide a transformer construction and mounting or installation therefor capable of wide adaptability of application to meet varying conditions or requirements met with in practical use.

Another object is to provide a transformer construction that will be simple, practical and dependable and yet well suited for the widely differing installation requirements met with, and thereby to avoid the expense, inconvenience, and

other difllculties attendant upon having to provide a special or particular transformer structure for each type or kind of mounting or installation. Another object is in general to improve upon transformer construction and mountings therefor and installations thereof. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts as will be exemplified in the structure to be hereinafter described and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings in which is shown a preferred embodiment of the transformer construction and several embodiments of mountings and installations, all by way of illustration:

Figure 1 is a perspective view partly broken away of a transformer casing section;

Figure 2 is a perspective view of a companion casing section;

Figure 3 is a perspective view of the transformer per se, namely the core and windings;

Figure 4 is a perspective view of an assembly and mounting device;

Figure 5 is a transverse sectional view of the transformer when installed according to one condition met with in practice;

Figure 6 is a sectional view through a wall box showing in end elevation another type of trans former mounting and installation according to 6 my invention;

Figure 7 is a perspective view of a barrier and mounting plate employed in Figure 6;

Figure 8 is a perspective view, on a smaller scale, of a different type of outlet or wall box adapted according to other features of my invention for a transformer mounting, and

Figure 9 is an elevation partly in section through the mounting plate as, for example, along the line 8-8 of Figure 6 or 99 of Figure 8, showing the interrelation between the transformer structure and the plate.

. Similar reference characters refer to similar parts throughout the several views in the drawmgs.

In Figure 3 I have shown a transformer T comprising a core l0 preferably laminated and illustratively of the shell type, being provided, therefore, with appropriate core windows and a central core leg I I through which and about which respectively the high and low voltage windings, generally indicated at l2, extend. Illustratively, the transformer may be for the purpose of reducing the volts of a household lighting circuit to a lower voltage, such as 15 volts, for operating relays, bells, buzzers, etc.

The laminations of the core l0 comprise individual appropriately shaped stampings appropriately laid together to build up the core about the windings I 2; the number of laminations and hence the thickness of core employed may vary according to the desired characteristics or capacity of the transformer, and according to certain features of my invention the casing structure later described is adapted to meet this variable circumstance.

The casing preferably comprises two principal sections, generally indicated at A and B in Figures 1 and 2, respectively. They are preferably of identical shape, each accommodated to cover half of the transformer T so that they may be initially stamped by the use of the same dies, thus avoiding multiple sets of different tools.

Thus, section A is formed to provide a marginal portion l3 of sufiicient expanse to rest against the face Ill (Figure 3) of the core III with its perimeter matching that of the face l0, and with the portion l3 resting flat against the outer portions of facelll. Four flanges l4, l5, l6 and H, at right angles to the plane of the part I3 and each extending from one of the four edges of the latter, relatively snugly overlap and'encase preferably not more than half of the sides of the core I0, acting also to hold the laminations of that fraction of the core l0 against shifting.

The inner portions of the portion |3 are drawn in a direction away from the flanges |4, |5, l6 and I1 to form the bulging portion l8 to take over the laterally projecting part of the windings l2 (see Figures 3 and 5). This bulging portion I8 may be given any suitable shape, illustratively and preferably the shape, of a frustum of a pyramid, and on one of the inclined sides there- 01', such as the side l9 in Figure 1, is mounted in any suitable manner, as by ears 2!) stamped out of the wall l9 itself, a suitable block or plate 2| of insulating material appropriately apertured as indicated for insulatingly guiding through suitable apertures in the wall IS the insulated conductors C that lead from the high voltageecoil of the windings l2. This inclined wall l9 permits the terminal conductors C and the insulating guiding means 2| to be provided without consequential obstruction of the marginal casing portion 13 adjacent to it.

In two opposed parts of the marginal casing portion I3, as in the parts l3 and I3 I provide narrow elongated slots 22 and 23; these may be and preferably are pierced in an operation separate from the stamping and forming steps in making up the sheet metal casing section A.

Casing section B is, as above'noted, identical to section A, having, therefore, a flat marginal portion l|3 to rest against the peripheral portions of the face Ill of the core- ID, with flang like parts H4, H5, H6 and M1 to take over the alined edges of the remaining half of the laminations of core l0, and thus, like the flanges I4, l5, etc., of section A, may, be individually bent and joined together at their edges or may be drawn to be continuous throughout; it has also arbulging portion H8, again preferably in the shape of a frustum of a pyramid, and in one of its inclined faces, such as face H9, it has secured thereto as by ears I20, an insulating plate or block |2| carrying connecting terminals 24 in the form of binding screws, the terminals having appropriate connection with the conductors E (Figure 5) which leadto the low voltage coil of the windings l2.

At two opposed portions of the marginal portion H3, as in the portions ||3 and H3 (Figure 2) I also provide slots and while they may be identical to the slots 22 and 23 of Figure 1, so that the piercing operation is the same, I prefer to provide in each portion two spaced slots 25, 26 and 21, 28.

When the two casing sections A and B are thus assembled to the transformer T, it being noted that the horizontal spacing between the flanges l1 and i5 and H1 and H5 is slightly greater than the horizontal dimension of the core l0, slot 22 is brought into juxtaposition to the spaced slots 25-26 and slot 23 becomes sim ilarly related to spaced slots 21-28, being thus made ready for the reception of two preferably identical securing and mounting devices, one of which is shown in Figure 4 where it is generally designated by the reference character F.

The device F is preferably made of sheet metal spaced to take respectively into the slots 25 and 26 or 28 and 21.

The portion 30, at its end remote from the tongues 3|, 32, is provided with suitable stop means to take against the marginal portion l3 of the casing section A, and that stop means may comprise spaced flanges 33, 34 which are preferably continued as at 33 and 34 along the extension 30" of the portion 30, extension 3!! being preferably tapered off or narrowed down as indicated, terminating finally in a transversely extending flange or foot 35 apertured as at 36, for a purpose later described. However, the extension 30 including the extensions 33 and 34 of the flanges, is preferably scored along the line S so that ultimately, when desired, this extended portion may be broken off as by the use of a pair of pliers.

The plate-like portion 30 has cut and bent out of it a relatively large tongue L, bent as shown to provide a crest or high point and of sufficient length and width, in relation to the metal of the part F, to give it a resiliency or springiness of action for a purpose later described.

Utilizing two such members F, one of them is passed through slot 22 in casing section and in between the face |0 (Figure 3) of the core I and the alined flange portions l1 and I I1 (see Figure 5), flanges 33 and 34 thereby being brought into engagement with the marginal casing portion l3, the ears 3|, 32 of member F having passed through the slots 25 and 26, respectively, in the marginal portion N3 of easing section B. In a similar manner (see Figure 5) the other of the two members F is passed through the slot 23 of section A, passing between the face W of the core l0 and the alined flange portions l5 and 5 of the two casing sections, lugs or ears 3|, 32 passing through slots 28 and 21, respectively.

With the two marginal casing portions l3 and- I I3 resting respectively against the marginal portions of the core faces l0 and III, the two casing parts are now suitably pressed toward each other, thus compressing the laminated core I0, and depending upon the number of laminations and hence thickness of the core, the juxtaposed edges of the two core-encasing flange casing parts l4, l5, etc., and H4, H5, etc., are brought more or less toward each other; thereupon, so much of the ears or lugs 3| and 32, there being four of them, as are left projecting beyond the marginal casing portion 3 are bent over, as shown in Figure 5, and against the adjacent side flanges which happen to be the parts 5 and N1 of easing section B. Thereby, the three parts, namely, the two similar casing sections and the transformer T, become securely and dependably assembled and with the laminations of the core snugly and tightly clamped against shifting or displacement.

As the two securing devices F are assembled as above described, the spring tongues L thereof, being bent as shown and above described, by-- pass the side flanges and remain spaced away from the alined side flanges |1--l l1 and |5-| l5, respectively, as is better shown in Figure 5.

If the transformer has to be mounted directly against or upon a flat supporting surface, as indicated at 31 in Figure 5, the flange or feet portions 35, falling in the same plane and spaced sufliciently away from the plane of the bulge l8, may be rested against the supporting surface and the transformer construction secured to the latter as by screws 38 passed through the apertures 36 in the feet. The low voltage terminals 24 are where the transformer construction has to be mounted in an outlet box, such as the box 40 of Figure 6, seated in a recess 4| in ,a wall 42 and provided "with suitable'lugs or angle plates 43 whereby, by theuse of screws 44 or the like, the box 40 may beheld in the recess 4| Where the box 40 is of usual or standard construction, it has lugs or ears, such as the ears. 45, provided with threaded holes-"spaced apart by astandard distance; in such'case, -I provide a plate 46 ofsuitably heavy sheet metalhaving at its upper end (see Figure 6) suitable flange-like means, such as a single flange '41, wh0se ends are apertured as iii) at .48 and areadapted to rest respectively upon the-supporting lugs or flanges of the outlet box 40 to bring the holes 48 in registry with the threaded holes in the lugs 45 for ultimate reception of the securing screws 49.

Preferably the plate 46 is dimensioned to flt and preferably I stamp a hole H (Figures '7 and 6) in the plate, giving it the length and breadth of the central casingportion that is made up of the alined flanges l4, 15, etc., and H4, H5, etc., of the casing sections A and B, but in two opposed edges thereof I provide recesses 50 and 5!, spaced and dimensioned to permit the turned over portions of the lugs 3|, 32 adjacent the low voltage face of the transformer freely to pass therethrough. Also, in each of these opposed edges of the hole H I provide a recess 52 of a length slightly greater than the width of the spring tongues L but the two recesses beingrespectively of such depths that the spacing between their bottom edges, as viewed in Figures 6 and 7, is less than the maximum spacingbetween the high points or crests of the two members L of the transformer structure as the latter is seen in Figure 5 or in Figure 9.

Accordingly, the transformer construction of Figure 5, preferably. with the leg extensions broken oil along the score lines S (see Figure 4) may be passed into the hole H in the plate 46, and in the case of the particular assemblage above described, with that end or casing section bearing the low voltage terminals 24 entering the hole H'first; the overturned lugs 3!, 32 pass through by way of the recesses 50, 5| whence the leading inclined portions of the two spring tongues L (see Figure. 5) enter the opposed recesses 52, and yieldingly resist continued passage of the transformer structure further into the hole H. However, as pressure is continued to be exerted, the tongues L, L,due to their springiness, yield'or are cammed inwardly toward the transformer casing walls, and thus the crests or high points of the tongues L are made to pass through the hole H and to the other side of the plate 46,

- their springiness yieldingly urging them outwardly again. However, passage of the transformer assemblage through the hole H is precluded since the flanges 33, 54 (Figure 4 and 9) project outwardly and act as stops to limit the extent to which the transformer construction can enter the hole H.

As is better seen from Figures 6-9, the end edges of these stop flanges terminate substantially in the plane of the marginal casing portion l4, thus bringing the plane of one face of the plate (see now Figure 9) into substantial alinement or coincidence with the plane of thecasing wall l3.

L urges them in a direction away'from each other, bringing an inclined portion of each into action against the bottom of the recess 52, thus tending constantly to cam and urge the plate and the stop flanges 33, 34 into contact and engagement with each other, and thus the assemblage is dependably maintained. a

The spring action of the parts L, L and their respective shapes may be so chosen that the as semblage of the transformer and the plate takes place with a sort of snap action. The ultimate holding action is a secure one, though disassemblage may be effected upon applying suflicient pressure to cause the tongues-L to yield to permit the transformer to be withdrawn from the hole H.

The mounting and barrier plate 45,with the transformer assembled thereto, may now be inserted into the box 40 and screws 49 employed to hold it in place. The low voltage terminal: 24 thereby become exposed in the space to one side of the plate 45 and the high voltage conductors or connectors C become exposed in the space cuit connections may be made in the usual way, the walls of the box 40 being provided with ap- The spring action of the latch-like tongues propriate knock-outs for'the entry and exit of the circuit conductors or' conduits. The flange 41 (Figures 6 and '7) preferably also has spaced threaded holes 55 spaced appropriately, usually by a standard distance, to receive screws 56 (Figure 6) by which a cover or finishing plate 5'! may be secured in position, constructed preferably so as to overlap the wall surfacing about the recess 4| in the wall.

Depending upon the character of the wiring system or other factors, other kinds or types of outlet or conduit boxes may be employed and to which the transformer has to be related; in Figure 8 one such other type of box is indicated at 58 by way of illustration and though shown to be generally round it may be in any other shape. For relating the transformer to such a box I employ a cover plate 59 apertured or slotted to receive the usual screws Bl] for securing the plate 59 in box-closing position, but the plate 59 is provided with a hole H shaped, dimensioned and recessed like the hole H above described in connection with Figures 7 and 9 and to the hole H the transformer may now be related in the same way as described above with reference to Figures 7 and 9. Then the resultant assemblage of transformer and plate 59, with the high voltage side and hence the high voltage conductors C facing inwardly toward the box and with the electrical connections thereto made, is related to the box 58, and the screws 60 are put in place to complete the mounting, leaving the low voltage side and terminals 24 exposed outwardly of the box whereby the low voltage circuit may be connected thereto. Here again, the leg portions or extensions of the member F of Figure 4 are preferably V on the other side of the plate 45; respective cir- I vided in this invention a transformer construction and mounting or installation therefor in which the various objects heretofore noted, to-

gether with many thoroughly practical advantages, are successfully achieved. It will be seen that I am enabled to have one transformer structure, itself of simple and inexpensive manufacture, serve in a simple and practical way to meet, due to simple and inexpensive coacting structural features, the widely varying requirements and peculiarities met with in practice. Manufacturing processes are greatly simplified and inventories to be carried by jobbers and electricians may be much smaller than has heretofore, according to past practices been possible.

It will also be seen that a minimum of different tools need be provided for manufacture of the devices, and by way of further example it will be seen that the hole H of Figures 6 and 7 may be punched in different plates by the same tool or tools.

. Referring back to Figures 1-5, the spacing between the alined side flanges l4-l I4 and iii-i I6 is preferably such as to snugly receive therebetween the vertical dimension of the core I0 as the latter is viewed in Figure 3, while the spacing between the remaining opposed alined sides, namely l'I-Jll and I5-II5, is preferably as is better shown in Figure 5, such that the horizontal dimension of the core I II, as viewed in Figure 3, plus the thicknesses of the two members F, is snugly receivable therebetween. When the lugs or ears 3l-32 are bent over, as shown in Figure 5, to hold'the laminations of the core clamped together with suflicient pressure, a strong and rigid transformer unit results for the two mem-- bers F dependably hold the two casing sections A and B against transverse displacement of one with respect to the other. The members F are likewise rigidly and solidly secured, thus permitting. dependable functioning of the parts F as supporting legs when the installation is as in Figure 5. Should the requirement be for a transformer of greater capacity so as to require a core ill of greater thickness, the same casing sections A and B maybe employed, the parts 3|, 32 being of suiiicient length to function with such greater thickness of core, and in such case there may be a greater spacing between the contiguous edge portions of the two casing sections.

In my co-pending application Serial No. 160,-

031, filed August 20, 1937, I have disclosed a transformer construction having certain subject matter in common with the transformer construction disclosed in my presentv application; it is in my said co-pending application that I make claim to such common subject matter.

As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to .be understood that all matter hereinbefore set forth, or shown in the accompanying drawings, is to be interpreted as illustrative and not in limiting sense.

I claim: a

1; In transformer construction, in combination, a transformer structure comprising a core and windings that project from two opposed side faces of said core and two casing sections having portions to rest against the marginal portions respectively of said side faces and respectively covering over the projections of said windings, means comprising at least two members that extend along opposed edge faces of said core and each having direct connection with each of said casing sections to hold them assembled to said core and to clamp'said sections and said core together, each of said two members having spring tongue means yieldably projecting therefrom each spaced from one of said edge faces and each of said members having stop means projecting in a direction outwardly from the adjacent edge face, a transformer-supporting plate having an aperture shaped to permit said transformer structure to be passed into it to an extent permitted by said 10 stop means, said spring tongue means yieldingas said structure is passed through the aperture to bring said stop means and plate in engagement v and acting to resist removal of the transformer structure from said aperture.

2. In transformer construction, in combination, a transformer structure comprising a core and windings that project from two opposed side faces of said core and two casing sections having portions to rest against the marginal portions respectively of said side faces and respectively covering over the projections of said windings, means comprising at least two members that extend along opposed edge faces of said core and each having direct connection with each of said casing sections to hold them assembled to said core and to clamp said sections and said coretogether, each of said two members having spring tongue means yieldably projecting therefrom each spaced from one of said edge faces and each of said members having stop means projecting in a direction outwardly from the adjacent edge face, whereby said transformer structure may be mounted in an aperture of a plate with the latter engaging said stop means and said tongue means holding the structure against such relative displacements as might bring said stop means and plate out of engagement, said two members having extensions provided with means whereby they may be secured to a wall surface or the like, said extension means being positioned and shaped so as not to interfere with the assembly of said transformer structure to said supporting plate.

3. A construction as claimed in claim 2 in which said two members are made of sheet metal and said stop means of each comprises flange means formed ,out of the sheet metal of each member.

4. In transformer construction, in combination, a transformer structure comprising a core and windings that project from two opposed side faces of said core and two casing sections having peripheral portions to rest against the marginal portions respectively of said side faces and respectively covering over the projections of said windings, two securing members each comprising a flat sheet metal portion having stop means at one end thereof, said two securing members overlying two opposed edge faces of said core, means comprising bent-over lug and slot means for securing said two securing members to opposed peripheral portions of said two casing sections, each of said securing members being provided with spring means exposed externally of the casing and core assemblage and presenting a crest spaced from said stop means.

5. In transformer construction, in combination, a transformer structure comprising a core and windings that project from two opposed side faces of said ,core and two casing sections having peripheral portions to rest against the marginal portions respectively of said side faces and respectively covering over the projections of said windings, two securing members each comprising a flat sheet metal portionhaving stop means at 7 one end thereof, said two securing members overlying two opposed edge faces of said core, means comprising bent-over lug and slot means for securing said two securing members to opposed peripheral portions of said two casing sections, at least one of said securing members having cut and bent out of said flat sheet metal portion a tongue having a projecting portion spaced from said stop means by a distance substantially equal to or less than the thickness of a supporting member for said transform er construction, whereby said supporting member may be yieldably gripped between said projecting portion of said tongue and said stop means.

6. In transformer construction, in combination, a transformer structure comprising a core and windings that project from two opposed side faces of said core and two casing sections having portions to rest against the marginal portions respectively of said side faces and respectively covering over the projections of said windings, said casing sections overhanging said core at two opposed edge faces of the latter and in the overhanging parts thereof being provided with registering slots, two securing members each comprisings a flat sheet .metal portion having stop means at one end thereof and lug extensions at theother end thereof, each member being passed through the slot in the overhang of one casing portion to the extent permitted by said stop means and having the lug extensions projected through the slots in the overhang of the other casing section to an extent accordingto the thickness ofthe core, said lug extensions being bent over to clamp saidcasing sections and core 0 bent out of the plane thereof tongue meanstogether, at least one of said casing sections having a flange-like extension overlapping the edge faces of said core and also said two securing members, said-securing members having cut and spaced from said stop means and overlying said flange-like casing extension.

7. A sub-assembly for installation in a wall box that has at its opposed upper ends flange-like means having threaded holes, said sub-assembly comprising a barrier plate of an expanse sufficient to fit the cross-sectional interiorof said box and having mounting means adapted to rest against said opposed flange-like means and to be secured thereto by screws threaded into said threaded holes, a transformer construction comprising a sheet metal casing receivable into said box but of smaller cross-section than the interior of the latter, said barrier plate having an aperture therein shaped substantially like that of a cross-section of said transformer construction whereby the latter is receivable into said aperture, said transformer construction having a plurality of sets of spaced holding means be- 0 tween which edge portions of said apertured barrier plate are received and of which one holding means of each set is positioned on one side of said cross-section to substantially limit the extent of entry of said transformer construction into said aperture and of which the other holding means of eachlset is positioned on the other side of said cross-section, at least one of them being resiliently yieldable and capable of yielding as said transformer construction is entered into said 7 aperture, thereby to hold said transformer con- 75 comprising a barrier plate of an expanse sumcie'nt to fit the cross-sectional interior of said box and having mounting means adapted to rest against said opposed flange-like means and to be secured thereto by screws threaded into said threaded holes, a transformer construction comprising a sheet metal casing receivable into said box but of smaller cross-section than the interior of the latter, said barrier plate having an aperture therein shaped substantially like that of a cross-section of said transformer construction whereby the latter is receivable into said aperture, said transformer construction having stop means positioned on one side of said cross-section to limit the extent of entry of said transformer construction into said aperture and having spring means positioned on the other side of said crosssection and capable of yielding as said transformer construction and said spring means are passed into said aperture to bring said stop means into engagement with said plate and thereafter holding said transformer construction against movement out of said aperture.

9. In transformer construction, in combination, a transformer structure comprising a core and windings that project from two opposed side faces of said core and sheet metal casing means enveloping said core and windings and having portions to rest against the marginal portions respectively of said side faces with bulges therein respectively covering the projections of said windings, and sheet metal means separate from said casing means and for mounting said structure onto a supporting surface, said last-mentioned means comprising two parallel sheet metal portions separate from said sheet metal casing means and extending respectively along and parallel to two opposed edge faces of said structure and each being of a width commensurate with the length of its adjacent edge face and of a length to extend beyond one of said bulges in said casing means to form supporting legs for engagement with said supporting surface and being provided with means for securing it to the supporting surface, said portions having flange means extending at an angle to the plane of the sheet metal thereof, said flange means reinforcing said portions against bending about an axis intersecting the flange means and lying in the plane of the sheet metal of the respective portions, and said flange means of said two parallel portions resting respectively against those portions of said casing means that rest against the marginal portion of one of said side faces of said core, and bent-over lug means to hold said parallel portions against movement in a direction to disengage said flange means from said casing means.

10. A construction as claimed in claim 2 in which said extensions of said two members are respectively joined to the latter by weakened portions whereby said extensions may be broken off when said transformer structure is mounted in the aperture of a plate as aforesaid.

11. In transformer construction, in combination, a transformer structure comprising a core and windings and a casing therefor that comprises at least two casing sections for respectively taking over substantially half portions of said core and windings, a plate for interrelation with said transformer structure, said plate having an aperture into which said structure is receivable, and means for securing said casing sections and core together, said securing means comprising two sheet metal members extending respectively along and substantially parallel to two opposed edge faces of the core, means connecting each mentioned spaced parts being resilient so that '11; yields as said transformer structure is entered 'into said aperture in order thereby to by-pass the edge portion of the plate.

12. In transformer construction, in combination, a transformer structure comprising a core and windings and a sheet metal casing therefor,

,said sheet metal casing having, at two opposed sides thereof, extensions forming spaced leg-like standards by which the structure may be secured to a supporting surface or the like, said two leg-like standards having weakened portions whereby they may be severed or broken ofl, each of said two extensions having, on the casing sides of said weakened portions, two spaced parts spaced apart by a distance substantially on the order of the thickness of an apertured mounting plate into whose aperture the transformer structure is insertable for support so as to receive opposed edges of the aperture between the spaced parts of said sides.

13. A transformer construction as claimed in claim 12 in which said extensions have each flanges to give them rigidity and to form at least one of the spaced parts of each of said opposed sides.

14. A transformer construction as claimed in claim 12 in which said extensions have each flanges to give them rigidity and to form at least one of the spaced parts of each of said opposed

Images